2023 Pre-assessment workshop for black rockfish in off Oregon

Disclaimer: All data summaries and exploration presented here are preliminary and may not be indicative of the final data that will be incorporated in the 2023 assessment models

Overview

Description of data and model specification being considered for use in the 2023 assessments for black rockfish off Oregon.

Summary of the 2021 Assessment

The last assessment of black rockfish rockfish in waters off of Oregon was conducted in 2015 and estimated stock status for that year at 60.4% (Figure \(\ref{fig:dep2015}\)), and never showed a decline below the target biomass (Figure \(\ref{fig:ssb2015}\)). This assessment was highly constrained by the choice to treat the catchability of the tagging index as known, thus the uncertainty in the assessment is very low. The complete assessment document can be found here.

Estimates of relative stock size (current spawning output/unfished spawning output) for black rockfish in waters off of Oregon from the 2015 assessment. Broken lines are 95% confidence intervals.

Estimates of spawning output (millions of eggs) for black rockfish in waters off of Oregon from the 2015 assessment. Broken lines are 95% confidence intervals.

Bridging the assessment model from Stock Synthesis 3.24 to 3.30

Since several years have passed from the last assessment model, the Stock Synthesis (SS) modelling framework has undergone many changes. While the specific changes in the model can be found in the model change log, here we simply update the model from the older 3.24V version to the newer 3.30.20 version. The point here is to present any differences in the model outputs when using the same information. This was first done by migrating the data and parameter specifications from the former files to the newer files. This migration was assisted using the SS-DL tool. Once the old data was transferred to the SS 3.30.20 file, two versions of the model were run.

1. fixing all parameter values to the values found in the 2015 model.
2. Allowing the same parameters estimation specification as in the 2015 model

Results are similar between models when all parameters are fixed from the 2015 model in the updated SS files, while there are slight scale differences (Figure \(\ref{fig:ssb_comps}\)), but little relative stock status differences (Figure \(\ref{fig:ssb_deps}\)), when the new SS version is allowed to estimate the same parameters as estimated in the 2015 version. Theses model comparisons are adequate to move ahead using the newest version of SS 3.30.20 without expecting large differences in reference models being due to versions of SS.

Comparison of spawning output for black rockfish in waters off of Oregon between Stock Synthesis versions 3.24 and 3.30. Uncertainty envelops are 95% confidence intervals.

Comparison of spawning output for black rockfish in waters off of Oregon between Stock Synthesis versions 3.24 and 3.30. Uncertainty envelops are 95% confidence intervals.

Unresolved Questions and Issues from the 2015 Assessments

1. Investigation the lack of older (> age 10) females in data. This affects the definition of natural mortality and selectivity values for females.
2. Improved historical catch reconstructions. The trawl fishery catches in particular need attention.
3. Identifying stanzas or periods of uncertainty in the historical catch series will aid in the exploration of catch uncertainty in future assessment sensitivity runs.
4. Treatment of the ODFW tagging study, mainly, the prior value on catchability.
5. Evaluate a nearshore survey.
6. Stock structure for black rockfish.

Stock Structure

The stock structure of black rockfish continues to be based on state-specific boundaries. Stocks definitions are based on a variety of factors that include genetics, biology, ecology, habitat availability and fishing mortality history. Black rockfish range from southern California up to Alaska. There ecology as a nearshore (i.e., commonly an area of restricted gene flow) rockfish with semi-pelagic behavior (e.g., can demonstrate rare, but substantial adult movements) under strong and differential fishing pressure by state provides an interesting assortment of considerations. A recent genetics study done by Hess et al. (in review) found that Alaskan and west coast populations showed significant genetic difference. The population from Washington to California showed a variety of interesting genetic signatures, with decreased genetic diversity north of Cape Mendocino and North of the Columbia River, but increasing in waters off of Oregon. There were also pockets of isolation by distance and odd signatures off Brookings, Oregon. These variable genetic signatures combined with the lack of consistent black rockfish habitat in southern Washington, and the different exploitation histories in each of the states made state-level designations to support management decisions the most logical. This does not suggest there is no exchange of individuals among California, Oregon and Washington, but instead acknowledges that the exchange is likely low enough not to homogenize the populations, and that different population trends can be expected in each state. This was supported in the results of the last assessment, where important differences in stock status were observed.

Fleet Structure

Currently, the following fleet structure is being considered for modeling commercial and recreational fisheries in both area models:

1. Commercial fixed-gear Fleet (dead and live fisheries combined)
2. Commercial trawl (mostly a historical fishery)
3. Recreational boat-based
4. Recreational shore-based

Defining fleets is largely based on whether a fishing approach differs in the selectivity (i.e., the capture of fish by length and/or age). Selectivity translates how the removals are taken via length and/or age out of the population. The above four fishery types are distinguished by different fishing activities that result in different selectivities. While in the past the commercial fixed-gear fisheries had been separated by the condition of the landed fish (dead and live), it has been determined that the designation of how the fish will be delivered is a processing issue, not a capture/selectivity issue. Thus the gear selectivity is considered the same in this fleet. This similarity in selectivity is apparent when looking at the 2015 assessment selectivity estimates. For the recreational fishery, the private and charter boat-based fisheries show similar aggregate length compositions and are treated as one fleet (Figure \(\ref{fig:private_charter_lts}\)). The boat- and shore-based fleets show distinct aggregate compositions that demonstrate the well known characteristic of shore-based landings catching smaller fish (Figure \(\ref{fig:boat_shore_lts}\)). These recreational fleets are the same treatments as in the 2015 assessment.

Aggregate length compositions of the private boat and charter boat fisheries. The compositions are not notably different, thus a combined boat-based fishery is used in the assessment.

Aggregate length compositions of the boat and shore-based fisheries. The compositions are notably different, thus a boat-based and shore-based fisheries are treated as separate fleets in the assessment.

Removal Data

Commerical Landings & Discards

Black rockfish are not considered a major commercial species, but historical reconstructions have shown prominent trawl catches in the past that have subsequently waned over the last 40 years. Historical catch reconstruction were done for the 2015 assessment, and are heavily based on applying highly variable catch compositions to years that do not have those composition, but rather just report total or “unknown” rockfish catches.

When providing data to the 2015 Black rockfish assessment, ODFW staff noted that trawl landings from the 1940s to the 1980s had high year to year variability and an unreasonable magnitude of landings in some years. These data were from the then newly completed Karnowski et al (2014) catch reconstruction. ODFW provided an alternative time series that was eventually used in the 2015 assessment (P. Mirick (ODFW) was the main source of this reconstruction). Additionally, the Karnowski et al. (2014) reconstruction did not account for fish taken off of Washington but landed into Oregon, specifically Astoria port landings. The Mirick reconstruction substantially reduced the magnitude of historic trawl catches and stabilized interannual variation in landings compared to the Karnowski et al. (2014) reconstruction. Total rockfish 3A landings were of similar magnitude between the two reconstructions, though different data sources were used in each approach. Species compositions, though, were from the same dataset (Douglas report), but differentially applied. The annual Douglas compositions were used for the Karnowski reconstruction, but these annual compositions were pooled for the Mirick reconstruction. Comparisons of 3A black rockfish from the Douglas report are different than in the Mirick reconstruction but of similar magnitude.

As a part of the 2015 assessment, trawl landings from 3A were also split between OR and WA by using the pooled Douglas compositions and other ODFW sources of information. Static average percentages of black rockfish were applied over multiple decades to allocate fish to WA. The STAT team is still considering the best magnitude of black rockfish in area 3A (dependent on the assumption of black rockfish composition within the to unknown rockfish category) to apply to this OR-WA split. The STAT is also considering further information that may confirm the level of black rockfish in 3A that are landed in Astoria but should be assigned to the Washington state history.

Commercial landings north and south of Point Conception. The landings are separated by fish landed live versus dead. The commercial landings in the south are relatively low (less than 10 mt per year) across the majority of years excluding 1995-1998 when landings ranged from 24 to 32 mt. The commercial landings in the north are generally higher than those observed south of Point Conception, particularly between 1983 to 1998 with landings peaking in 1993 at 69 mt (sources: PacFIN and California historical catch reconstruction).

Proportion of commercial landings from fish landed dead north and south of Point Conception in recent years (source: PacFIN).

 

Landings by area, time period (grouped by decade), and gear grouping (source: PacFIN).

 

Additional Items for Discussion

Only the commercial landings are shown for each area. Discard mortality across time will need to considered to determine catches.

• The 2021 assessments assumed a constant discard mortality rate of 4.4% informed by WCGOP data for each area in California.
• The rate of discarding has likely varied across time. Are there particular periods of time when discarding likely increased/decreased?
• Different factors impacting discarding practices by area?

Recreational Landings & Discards

The recreational landings

Recreational landings (in mt) for the ocean boat-based fleet used in the 2015 versus that proposed for the 2023 assessment.

Recreational landings (in mt) for the shore-based fleet used in the 2015 versus that proposed for the 2023 assessment.

Additional Items for Discussion

Indices of Abundance

Fishery-Independent

NWFSC Hook and Line Survey

T ### NWFSC West Coast Groundfish Bottom Trawl Survey

Fishery-Dependent

Composition Data

Commerical length compositions

The number of length samples by year from live and dead copper rockfish from the area south and north of Point Conception. Since 1981, there are a total of 3,517 dead and 1,099 live length samples north of Point Conception and 553 live and 2,135 dead length samples south of Point Conception (source: PacFIN).

The majority of lengths are from hook and line gear for each area:

• North of Point Conception (total lengths = 4,616):
  • 4,268 from hook and line gear,
  • 32 from net gear,
  • 139 from pot gear,
  • 15 from troll gear, and
  • 162 from trawl gear.
• South of Point Conception (total lengths = 2,688):
  • 2,585 from hook and line gear,
  • 24 from net gear,
  • 39 from trawl gear, and
  • 36 from shrimp trawl gear.

The distribution of length samples by year from live and dead copper rockfish from the area south and north of Point Conception. The black horizontal line within each box indicates the median length observed that year where the median is defined as an equal number of observations from that year that are greater than and lesser than that value. The lower range of each box indicates the 25th percentile where 25 percent of observations that year are less than that length. The upper range of each box indicates the 75th percentile where 75 percent of observations that year are less than that length (source: PacFIN).

The density of size selected by landed condition, live or dead, for each area across all years (source: PacFIN).

Boxplot of lengths by landed port, area, and fish condition (live or dead). Only ports with greater than 100 length samples (live + dead > 100 samples) across all years are shown (source: PacFIN).

Recreational length compositions

The recreational length composition data summarized below represen data pulled from RecFIN collected by either the MRFSS (1980 - 2003) or CRFS (2004 - 2022) sampling programs. There are additional data sources that contain historical length samples from the CPFV fleets (1975-1979 from Collins and Crooke, 1987-1998 from Deb Wilson-Vandenberg, and 1986-1989 from Alley and Ono) that will be evaluated and used within each assessment model as appropriate but are not included here.

The total number of length samples within RecFIN across MRFSS and CRFS are:

• North of Point Conception (total lengths = 38,994):
  • 11,969 from CPFV, and
  • 27,025 from Private/Rental vessels.
• South of Point Conception (total lengths = 31,036):
  • 23,535 from CPFV, and
  • 7,501 from Private/Rental vessels.

In RecFIN there are lengths from shoreside modes that were not included in the analysis presented below (north of Point Conception = 148 and south = 20). All lengths below represent released fish. There were limited length observations of released fish (north = 52 and south = 187).

The number of length samples by year and mode for copper rockfish for areas south and north of Point Conception. Since 1980, there are a total of 11,969 CPFV and 27,025 Private/Rental length samples north of Point Conception and 23,535 CPFV and 7,501 Private/Rental length samples south of Point Conception (source: RecFIN).

The density of size selected by mode, CPFV or Private/Rental, for each area across all years (source: RecFIN).

TODO: Add table and figures showing the around the number of single day and multi-day trips

Survey length compositions

Biology

Maturity and Fecundity

TODO: Add figure showing the two maturity curves from last assessment.

TODO: Add fecundity-at-length figure based on Dick et al. that was assumed in the last assessment

TODO: Add information on additional maturity and fecundity samples being collected that will be used to update both maturity and fecundity if information is available in time.

Length-Weight

The length-weight relationship was estimated using all biological data available from the NWFSC West Coast Groundfish Bottom Trawl (WCGBT) and the NWFSC Hook and Line surveys.

Length weight relationship by sex for copper rockfish (source: NWFSC WCGBT and HKL Surveys).

Length-at-Age

TODO: Add plot showing the length-at-age of available data by area

TODO: Add table of the number of additional age reads by sources that the CAP lab is working on

Natural Mortality

Natural mortality was fixed in the 2021 assessments at a value of 0.108 yr^-1 based on an assumed maximum age of 50 years. The maximum age was selected based on available age data collected within Oregon and Washington and literature values. The oldest aged observed was 51 years with two observations off of the coast of Washington and Oregon in 2019. This selection was consistent with the literature examining the longevity of copper rockfish and was supported by the observed ages that had multiple observations of fish between 44 and 51 years of age.

The input parameter value for natural mortality will be reconsidered within the 2023 assessments based on any new available age data. Additionally, the 2023 assessments will explore the ability to estimate natural mortality within the model and will conduct sensitivities and profiles to understand the information in the data on natural mortality and the impact of select values on the model estimates.